The present invention relates to a solar panel.
The present invention also relates to a device for collecting solar energy in thermal form.
The present invention further relates to a method for realizing the structural solar panel.
Solar panels integrating photo-voltaic cells are known. They are expensive, require elaborate production facilities and produce relatively modest amounts of energy.
Panels are also known which are designed to produce a greenhouse effect by transforming the solar radiation received on an outer face of the panel into thermal radiation emitted by the opposite face.
GB-A-1 467 039 describes a panel having on one face a tubular network for a heat-transfer fluid, and an aluminum sheet thermally linked to the copper tubular network. The whole is held against a thermally insulating layer by screwed profiled sections. The solar energy is collected in the form of an increase in temperature of the heat-transfer fluid.
According to FR-A-2 384 215 the screwed profiled sections are replaced by a front plate and the tubular network is an integral part of the thermally conductive sheet.
Such panels are expensive to realize and require a bearing structure. The sheet or other thermally conductive layer is not compatible with the realization of structural composite panels such as sandwich panels where a central core typically made of foam is sandwiched between two plates of preferably thermo-setting synthetic resin which are reinforced with a sheet of glass or synthetic, woven or non-woven fibres.
An aim of the present invention is to propose a panel for collecting solar energy which is particularly economical to produce and effective in energy-creating and mechanical terms, and allows easy installation.
Another aim of the present invention is to propose a device for collecting solar energy which is economical and effective.
According to a first aspect of the invention, the solar panel comprising:
a front plate situated on the side exposed to the sun;
a thermally insulating layer adjacent to a rear side or face of the front plate, facing away from exposure to the sun;
a tube bundle for the circulation of a heat-transfer fluid, this bundle being interposed between the front plate and the insulating layer; and
a thermally conductive sheet interposed between the front plate and the thermally insulating layer and which is thermally linked to the front plate and to the tube bundle;
xe2x80x83is characterized in that the thermally conductive sheet is permeable to an agent binding the frontal plate with the thermally insulating layer and forms an integral part of an interface stratifying the front plate with the thermally insulating layer.
A structural panel is thus realized where the thermally conductive sheet actually reinforces the stratification interface. The cost of production is not greatly increased compared with a standard structural panel and fitting is the same apart from the connection to a fluid circuit. In particular, the panel can be self-supporting and thus not require a bearing frame.
It has been shown that a particularly suitable thermally conductive sheet consists of a metal grille, preferably of aluminum, or of a sheet of thermally conductive fibres, in particular carbon fibres.
The panel is preferably of the sandwich type, the insulating layer being arranged between the said front plate and a rear plate.
It is advantageous that the tubular network is a flexible tube, for example of synthetic material, that is arranged in a sinusoidal duct formed in the insulating layer is to form a coil. It has been found that the tubular network did not need to be made of material that was thermally very conductive, since the collected heat is properly trapped and conveyed by the conductive sheet. It has proved very advantageous in this respect that the sheet extending substantially along the front plate forms housings for locally bypassing each element of the bundle by passing between the bundle and the insulating layer. Thus, each element of the tubular network receives heat, on the one hand directly from the front plate on the front face of the tube or tubes, and on the other hand via the sheet on the remainder of the circumference of the tube or tubes.
According to a second aspect of the invention, the device for collecting solar energy in thermal form is characterized in that it comprises:
a tank of heat-transfer fluid;
a pump having an inlet immersed in the heat-exchange fluid of the tank; and
a panel incorporating a tube bundle for the heat-transfer fluid, the panel being arranged at an angle relative to the horizontal such that the tube bundle has an upper end connected to the outlet of the pump, and a lower end opening out freely above the level of fluid in the tank.
Such a device drains easily when it has stopped, through reversal of the flow. The reverse flow is then from the lower end to the upper end and from there into the tank through the pump. Such a drainage can take place through reversal of the direction of operation of the pump. Drainage is even automatic and spontaneous as soon as the pump stops on condition that the pump is of a type where the inlet and the outlet communicate with each other at least when the pump has stopped. This is typically a pump of the centrifuge type or other pump of the rotor-turbine type.
Thus the device according to the invention is particularly suitable for use with the solar panel housed in the roof. Moreover, the heat-exchange fluid can comprise water without this resulting in a risk of degradation through frost or limescale.
For preference:
the device for collecting solar energy comprises thermostatic means for interrupting the operation of the pump when a recorded temperature of use, such as for example the temperature of the heat-transfer fluid in the tank, exceeds an upper threshold value, and/or for interrupting the operation of the pump when the temperature of the front plate is below a lower threshold value.
means are provided to vary the lower threshold value in relation to a recorded temperature of use, such as for example the temperature of the heat-transfer fluid outside the tubular network and in particular in the tank.
the tank is a pool.
According to a third aspect of the invention, the method for realizing a panel according to the first aspect comprises: forming at least one duct in one face of a flat foam block, placing the conductive sheet on the said face of the block, placing a tubular network in the duct while the sheet forms housings copying the shape of the duct, then fixing a front plate on the said face by means of a structuration interface.
Other particular features and advantages of the invention will also emerge from the description below, relating to a non-limitative example.
In the attached drawings:
FIG. 1 is a view in section and perspective of a panel according to the invention;
FIG. 2 is a view in cross-section illustrating a stage in the production process of a solar panel according to the invention:
FIG. 3 is a view of a detail of a panel, in section; and
FIG. 4 is a view of a collecting device according to the invention.